Script point light strength in cycles
You can do this by adding an event handler to the frame change event.

import bpy

def my_handler(scene):

    fm = bpy.data.scenes['Scene'].frame_current

    if fm &gt;= 1:
        lampStrength = 100
    if fm &gt;= 50:
        lampStrength = 200
    if fm &gt;= 100:
        lampStrength = 300
    if fm &gt;= 150:
        lampStrength = 400                

    scene.objects['Point'].data.node_tree.nodes['Emission'].inputs['Strength'].default_value=lampStrength

    print("lamp strength: " + str(lampStrength))


def register():
    bpy.app.handlers.frame_change_post.append(my_handler)

def unregister():
    bpy.app.handlers.frame_change_post.remove(my_handler)

if __name__ == "__main__":
    register()    


Credit for frame change portion of script here: Running a script for each frame